This invention relates to a high speed dental drill, and more particularly to a high speed dental drill having contamination prevention means and an improved drive for high speed operations.
High speed, air-driven dental drills are known in the art, for example as disclosed in U.S. Pat. No. 4,203,221. With such dental drills, air enters the turbine area through an opening in the handpiece and passes over the rotatable vanes or blades that are secured to the outside of a rotor, thereby rotatably driving the drilling tool fixedly mounted to the rotor. However, such dental drills have relatively inefficient drive assemblies. As a result, it has been necessary to use a high velocity air stream to drive the rotor at high speeds. In practice, such drills rotate at speeds between about 320,000 rpm and about 500,000 rpm.
In order to avoid discomfort to the patient and so as not to interference with the drilling operation, it has been necessary to exhaust the high velocity air stream through an opening in the casing which does not face the patient, so that the exhausted air does not impinge on the patient. A typical construction for exhausting the spent drive air in a turbine-type high speed dental drill is shown as exhaust channel 75 in FIG. 5, which will be discussed further hereinbelow.
A recent problem, however, has arisen with respect to such high speed drills. Specifically, it has been found that, due to the high speed rotational nature of the drilling tool, there is a tendency for blood and other human fluids in the patient's mouth to be drawn up the drilling tool into the drill head. This primarily occurs at turn off of the compressed air drive source when the drill is to be turned off. At such time, suction forces are developed internally of the drill head due to inertia of the turbine member 134 which causes it to continue to rotate after turn off of the drive air. Accordingly, when the drill is used on the next patient, the blood or other human fluids from the prior patient's mouth, which had been drawn up into the drill head by such suction forces, can ride or flow down into the next patient's mouth. Thus, for example, if the first patient is HIV-positive, or carries other infectious diseases, the next patient can be contaminated with the HIV-positive (or otherwise contaminated) blood from the first patient.
Although this can be avoided by sterilizing the drill head after each use in an autoclave, the majority of dentists do not autoclave the drill head after each such use, but rather, at most, do so only at the end of each day or a few times during the day. Some practitioners also dip the drill in a disinfectant or wipe the drill head with disinfectant after each use. These precautions are not sufficient. Such superficial "cleaning" is usually done because if autoclaving is carried out after each use, the dentist would be required to purchase additional drills and drilling tools to use on the next patient while the autoclaving process is occurring with respect to the drill and drilling tool from the prior patient. This could increase the cost of the dental supplies to the dentist by many thousands of dollars. Moreover, autoclave sterilization between uses is only recommended, not required, by the American Dental Association. Accordingly, as described above, the majority of dentists merely wipe the outside of the drill head with a disinfectant between uses. This, however, does not eliminate the contaminated blood or other mouth fluids that have been drawn up inside the drill head.
It is an object of the present invention to provide an improved high speed dental drill in which positive air pressure is provided and maintained inside of the drill head so that the air used to power the turbine is positively exhausted, by the positive air pressure, toward the drilling tool so as to prevent contaminated blood from being drawn up into the drill head both during operation and during turning off of the drill.
A further object of the invention is to provide such an improved high speed dental drill in which the turbine can be driven with less air power so that the exhausted air is not uncomfortable to the patient and does not interfere with the drilling or other dental operation.